SAN FRANCISCO (AFP) - Google on Thursday unveiled its pay-with-a-phone system for Android devices, ramping up its challenge to Apple in mobile payments.

Android Pay, unveiled at the Google Developers conference in San Francisco, brings together mobile carriers, payment networks, banks and retailers to allow smartphone users to use their handsets instead of payment cards.

Google engineering vice president Dave Bruke said Android Pay would work in more than 700,000 US retail outlets that accept contactless payments.

"We are at the start of an exciting journey, we are working closely with payment networks, banks and developers," he said.

A Google blog post said the system was in partnership with the major credit card firms including Visa and Mastercard and payment processing firms including Braintree, CyberSource, First Data, Stripe and Vantiv.

Similar to the Apple Pay system unveiled last year, Android Pay will allow consumers to store their credit card information on their handsets along with loyalty cards and other data.

For extra security, Android Pay will generate a one-time "token" or virtual account number so the actual credit card data is not revealed in a transaction.

"Users can simply and safely use their Android phone to pay in stores where you see an Android Pay logo," Burke said.

"We are focused on simplicity, security and choice." Google said in February it was teaming up with the mobile phone payment firm Softcard to ramp up its efforts in the emerging sector.

This will allow Google Wallet to become a pre-installed "tap to pay" app on Android smartphones.

No date was announced for Android Pay but the Google statement said it would be "available on Google Play for download soon."